Tie down with automatic strap tension adjustment

ABSTRACT

A tie down apparatus wherein a center leg of each of a pair of load springs is mounted in the space between a pair of drum pins, which space receives and holds a tied down strap. Each load spring is fixedly attached to a respective one of first and second ratchet wheels and a circular plate is positioned within each ratchet wheel and configured to rotate through a selected arc with respect to each ratchet wheel to limit the pre-load applied to the load springs.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/900,587 of the same title and filed Feb. 20, 2018, which applicationis incorporated by reference herein in its entirety.

BACKGROUND Field

The subject disclosure relates to tie down mechanisms and moreparticularly to a tie down mechanism featuring automatic adjustment ofthe tension applied to a strap component of the mechanism.

Description of Related Art

Various tie down mechanisms have been constructed in the past and havebeen employed, for example, to tie down a load to a trailer or othertransport vehicle. In such applications, such tie down mechanismstypically have a first strap which is secured to the load and a secondstrap which is attached to the trailer.

SUMMARY

According to an illustrative embodiment, a tie down apparatus includes adrum comprising first and second drum pins separated by a space, thespace being shaped to receive and hold a tie down strap as well as firstand second ratchet wheels, the first and second ratchet wheels eachcomprising a plurality of ratchet teeth.

First and second spiral load springs are each mounted adjacent anoutside surface of one of the first and second ratchet wheels. Eachspiral load spring has a center leg and a tab at an outer end thereof.In the illustrative embodiment, the center leg of each spiral loadspring is inserted in the space between the first and second drum pins,and the first end of each tab of each spiral load spring is fixedlyattached to a respective one of the first and second ratchet wheels,such that as the ratchet wheels are rotated, a preload is applied to thefirst and second load springs.

Further in the illustrative embodiment, first and second circular platesare mounted in a central opening in each ratchet wheel and have firstand second openings shaped to respectively receive opposite ends of thefirst and second drum pins. The ratchet wheels have inwardly projectingnubs positioned to come into engagement with outwardly projecting nubson the first and second circular plates as each ratchet wheel rotateswith respect to its respective circular plate. In an illustrativeembodiment, these nubs interact so as to limit the amount of pre-loadapplied to each load spring.

According to the illustrative embodiment, rotation of the ratchet wheelsto tighten the tie down strap pre-loads the spiral load springs to thesame tension applied to the strap up to a limit established by theinteraction of the respective nubs of the ratchet wheels and circularplates. If the strap were to lose tension below the preload spring rateof the spiral springs, then the springs act to force the drum pins torotate and increase tension on the strap until the preload tension ofthe springs and the strap tension are in equilibrium or until thesprings have lost all of their preload.

According to another aspect of the disclosure, a method of strap tensionadjustment for a tie down apparatus is provided comprising attaching anouter end of first and second load springs to respective outsidesurfaces of respective first and second ratchet wheels, inserting aninner leg of each load spring into a space between respective rotatingpins of the tie down apparatus, positioning a plate within a centralopening in each ratchet wheel, and configuring each plate to rotate inunison with the respective rotating pins. Further according to themethod, an inner periphery of each of the ratchet wheels and an outerperiphery of a respective one of the plates are shaped such that theinner periphery and outer periphery interact so as to stop rotation ofthe first and second ratchet wheels with respect to the plates at aselected point so as to limit an amount of pre-load force applied to theload springs.

According to another aspect of the disclosure, first and second platesare each sandwiched between the outside surface of a respective one offirst and second ratchet wheels and an inside surface of correspondingspiral load springs, each spiral load spring having a center leg and atab at an outer end thereof, wherein the tabs and respective ratchetwheels are configured to rotate in unison together through a first rangeof motion and wherein the center leg of each of the first and secondload springs is positioned in the space between the drum pins of a tiedown apparatus. Each of the first and second plates has a cut-out arcportion in its perimeter having first and second end surfaces, and thetab of each spiral load spring is positioned to move within the cut-outarc from the first end surface to the second end surface, such that, asthe first and second ratchet wheels are driven in a direction so as totighten a tie down strap, the tab of each spiral load spring is driventoward the second surface until it abuts that second surface. After suchabutment, the first and second ratchet wheels are constrained to rotatein unison with the first and second plates such that no further load isapplied to the spiral load springs. In one embodiment, each tab isfixedly attached in a slot in each respective ratchet wheel. In anotherembodiment, each tab engages a bump formed on each respective ratchetwheel. In another embodiment, each tab is step-shaped and is insertedinto a mating step-shaped opening in a respective ratchet wheel

DESCRIPTION OF THE DRAWINGS

FIG. 1 is front perspective view of a tie down apparatus according to anillustrative embodiment in a first position;

FIG. 2 is a rear perspective view of the tie down apparatus of FIG. 1;

FIG. 3 is an exploded view of the tie down apparatus according to theillustrative embodiment;

FIG. 4 is a perspective view of tension adjustment apparatus accordingto an illustrative embodiment in an assembled state;

FIG. 5 is an exploded view of the tension adjustment apparatus of FIG.4;

FIG. 6 is a front perspective view of the tie down apparatus of theillustrative embodiment in a second position;

FIG. 7 is a rear perspective view of the tie down apparatus of FIG. 6;

FIG. 8 is a perspective view of the tie down apparatus of theillustrative embodiment in a third position;

FIG. 9 is a perspective view of the tie down apparatus in a fourthposition;

FIG. 10 is a side view of the tension adjustment apparatus of FIGS. 4and 5.

FIGS. 11 and 12 are perspective views illustrating another embodiment oftension adjusting apparatus;

FIG. 13 is a perspective view illustrating another embodiment of tensionadjusting apparatus; and

FIG. 14 is a perspective illustrating another embodiment of tensionadjusting apparatus.

DETAILED DESCRIPTION

FIGS. 1-10 show an illustrative embodiment of a self-adjusting tie downapparatus 11. The illustrative embodiment 11 includes a base frame 13,which is attached to a fixed strap 112 (FIG. 7) secured by a bolt 15 andnut 17. A “drum” 18, which comprises two drum pins 19, 21, rotates inrespective circular openings 50 in respective end plates 29, 31 of thebase frame 13. This drum 18 is caused to rotate by respective centerlegs 123 of respective main load springs 125, one spring 125 on eachside of the drum 18 and positioned adjacent the outer sides ofrespective first and second ratchet wheels 135. A tab 136 at the outerend of each main load spring 125 is inserted into a slot 142 in the sideof each ratchet wheel 135 and, in one embodiment, is fixedly attached tothe respective ratchet wheel 135, for example, by welding.

In an illustrative embodiment, each main load spring 125 is a spiralwound spring. A circular plate 148 is centered within each ratchet wheel135, as shown for example in FIG. 5. In the illustrative embodiment,each circular plate 148 is positioned between a respective load spring125 and one of the end plates 29, 31 of the base frame 13 and is therebyheld in place axially.

In the illustrative embodiment, the interior circular periphery of eachratchet wheel 135 has three radially positioned inwardly projecting nubs151, 153, 155 formed thereon separated from one another by 120 degrees.Correspondingly, each circular plate 148 has three radially positionedoutwardly projecting nubs 152, 154, 156 formed on its outer circularperiphery and separated from one another by 120 degrees. The componentsare sized such that the nubs 152, 154, 156 of each circular plate 148will come into contact with the nubs 151, 153, 155 of the respectiveratchet wheels 135 if the ratchet wheels 135 are rotated through aselected arc with respect to the circular plates 148. Each circularplate 148 further has slots 232, 234, which receive the ends 20, 22 ofthe drum pins 19, 21 and are shaped conformably such that the circularplates 148 are forced to rotate in unison with the drum pins 19, 21.

In assembly of the apparatus of FIG. 5 according to an illustrativemethod of assembly, the drum pins 19, 21 are first inserted into theopenings 50 in the end plates 29, 31 of the base frame 13. Each loadspring tab 136 is then welded or otherwise attached to its respectiveratchet wheel 135. Each circular plate 148 is then slid onto theopposite ends of the drum pins 19, 21. The springs 125 with ratchetwheels 135 attached are then mounted onto opposite ends of the drum pins19, 21 by placing the leg 123 of each spring 125 in the slot 57 betweenthe drum pins 19, 21 and pushing the legs 123 into the slot 57, whileallowing each circular plate 148 to come into position within itsrespective ratchet wheel 135. In one embodiment, an end cover 126 may beslid over the outer periphery of the load spring 125 and ratchet wheel135 to cover the assembly.

Each side of the base frame 13 has an angled slot 37 into which fitsrespective wings 40 of a main latch 39. The main latch 39 can slide inthe slots 37 and engage the teeth, e.g. 41, of each ratchet wheel 135and is spring loaded toward each ratchet wheel 135 by a main latchspring 43 (FIGS. 3, 8). The main latch spring 43 is mounted on a pin 146projecting from a rear side of the main latch 39 and is held in place byan upright projection 42 on the base frame 13, which has a slot 44 (FIG.3) through which the pin 46 fits.

A handle frame 45 has circular openings 150 (FIG. 3) through whichproject the respective ends, e. g. 20, 22, of the drum pins 19, 21. Twopins 47 respectively inserted through the drum pins 19, 21 on eitherside of the device serve to hold the mechanism together.

The handle frame 45 has a handle 49 at one end that is easy to grip anda pair of slots 51 in which fit respective wings 54 of a handle latch53. The handle latch 53 slides in the slots 51 and engages respectiveteeth, e.g. 41 b (FIG. 1), of each ratchet wheel 135. The handle latch53 is spring loaded toward the ratchet wheel 135 by a handle spring 55(FIG. 3). The handle latch 53 has a slot 56 in which fits one end 58 ofthe handle spring 55, while the coiled end 60 of the handle spring 55fits over and is retained by a pin 62 formed in the slot 51 of thehandle frame 45.

The tie down 11 is used by inserting a strap 12 through the slot 57 inbetween the two drum pins 19, 21, as shown in FIG. 6. As shown in FIG.2, in a first position, the main latch 39 is engaging a tooth 41 c ofeach of the ratchet wheels 135, specifically by engagement with thefront surface of those two ratchet teeth, e.g. 41 c. As shown in FIGS. 1and 2, in the first position, the handle frame 45 is at its lowest pointof rotation, lying generally parallel to the base frame 13. In thisposition, rear surfaces 160 of the respective recesses 59 (FIG. 3) ofthe handle frame 45 engage the respective wings 40 of the main latch 39and prevent the main latch 39 from disengaging from the ratchet wheelteeth, e.g. 41 c.

Additionally, in the first position shown in FIGS. 1 and 2, each surface74 of the spring loaded handle latch 53 is engaging each ratchet wheel135 via engagement with the front surface of a respective oppositelydisposed pair of ratchet teeth, e.g. 41 b. In this position, therespective surfaces 74 on the handle latch 53 are also locked behind arespective step 61 formed on the circumference of the base frame 13,which prevents the handle latch 53 from rotating around the drum 18.

As illustrated in connection with FIG. 6, by pulling the handle 68 ofthe handle latch 53 against its spring bias away from the base frame 13in the direction of arrow 70, the surfaces 74 on the handle latch 53will clear the steps 61 in the base frame 13, and the handle frame 45can then rotate into a second position shown in FIGS. 6 and 7. Thisaction also clears wings 40 of the main load latch 39 from engagementwith the rear surfaces 160 of the recesses 59 such that the main loadlatch 39 is now free to slide back and forth in its respective slots 37while engaging the teeth, e.g. 41 c, on each ratchet wheel 135.

By rotating the handle frame 45 through an arc from the second positionto the third position shown in FIG. 8, each ratchet wheel 135 willrotate through the same arc. In an illustrative embodiment, this arcamounts to three ratchet teeth out of eleven total=an arc ofapproximately 98 degrees. This rotation causes each main load spring 125to rotate the drum pins 19, 21 through the same angle, as long as thereis no tension load on the strap 12. At the same time, the main loadlatch 39 shuttles back and forth following the rear cammed or contouredsurfaces 76 (FIGS. 2, 4, 5) of three successive ratchet teeth 41 of eachratchet wheel 135, thus “ratcheting” three times in the illustrativeembodiment. At the end of this ratcheting action, the main load latch 39again engages behind the flat surface of the next successive ratchettooth of each ratchet wheel 135, as shown in FIG. 2.

After the handle frame 45 reaches the third position of FIG. 8, it isrotated from the third position back to the second position while thehandle latch 53 slides back and forth following the rear profile 76 ofeach ratchet wheel tooth, again “ratcheting” three times and engaging atthe end of the travel behind the flat surface of another pair of ratchetteeth. During travel from the third position back to the secondposition, the drum pins 19, 21 do not rotate, and the tension on thestrap is maintained by the main load latch 39.

This process of rotating the handle frame 45 between the second andthird positions will continue and in turn will put additional load onthe strap 12, and therefore each main load spring 125 will also bepreloaded to the same level of tension. As each main load spring 125 ispreloaded, each nub 151, 153, 155 of each ratchet wheel 135 begins torotate toward the corresponding nub 154, 156, 152 of each circular plate148 as illustrated in FIG. 10. In this respect, nub 151 approaches andeventually comes into abutment with nub 154, nub 153 approaches andeventually comes into abutment with nub 156, and nub 155 approaches andeventually comes into abutment with nub 152.

In an illustrative embodiment, if the nubs are each 10 degrees “wide,”(Tab 1, Tab 2 angles), then the maximum angular rotation of the ratchetwheels 135 before the nubs of the ratchet wheels 135 engage the nubs ofthe circular plates 148 is 120 degrees minus 20 degrees equals 100degrees. When the nubs so engage, the ratchet wheels 135 are preventedfrom rotating further with respect to the circular plates 148 and thepins 19, 21, and further loading of the load springs 125 ceases. At thispoint, the load springs 125 have reached the maximum preload permittedby the particular design of the device. In an illustrative embodiment,the maximum angular rotation during which preload is applied is 100degrees, but may range from 40 to 340 degrees in other embodiments,depending, for example, on the type of spring tension selected, numberof nubs, and the application for which the tie down is used. In otherembodiments, the circular plates 148 and ratchet wheels 135 could eachhave less than three nubs respectively, for example, two nubs on each ofthe circular plates 148 and ratchet wheels 135, or one nub. Thus, forexample, each circular plate 148 may have at least one outwardlyprotruding nub and each ratchet wheel 135 may have at least one inwardlyprotruding nub.

Once each main load spring 125 has gone through an approximately 100degrees preload angle, further preload on the main load springs 125ceases in order to prevent overloading those springs 125, and anyfurther tension generated by rotating the handle frame 45 from thesecond to the third position will now in turn directly rotate the drumpins 19, 21, and add additional load tension to the strap 12. When thetie down operation is complete, the tie down 11 is in the lockedposition shown in FIGS. 1 and 2.

In the event that the strap 12 were to lose tension below the preloadspring rate of the main load springs 125, then the main load springs 125will force the drum pins 19, 21, to rotate and increase tension on thestrap 12 until the preload tension of the main load springs 125 and thestrap tension are in equilibrium or until the main load springs 125 havelost all of their preload.

As shown in connection with FIG. 9, when the apparatus is in theposition shown in FIG. 8, pulling on the handle latch handle 68 againstits spring bias further in the direction of the arrow 70 allows thehandle frame 45 to move into a fourth position shown in FIG. 9. Thisaction disengages the handle latch 53 from the ratchet wheel teethcompletely. At the same time, a ramp 101 on the exterior of the handleframe 45 also pushes the main load latch 39 away from the ratchet wheelteeth 41. This effectively allows the drum pins 19, 21 completely freerotation, removes the tension on the strap 12, and releases anyremaining tension on the main load springs 125.

FIGS. 11-14 illustrate alternative embodiments for enabling the ratchetwheels of the tie down mechanism to first rotate freely with respect tothe load pins 19, 21 and to thereafter stop that free rotation at apoint after the spiral springs have been loaded to a degree whichenables maintaining tension on the strap of the tie down mechanism. Inan embodiment illustrated in FIGS. 11 and 12, a plate 248 has a cut-outarc 249, which provides two surfaces designated “A” and “B.” A first tab236 at the end of a spiral load spring 225 is fixedly attached in anotch or opening 242 in a ratchet wheel 235, while the inner end 223 ofthe spiral load spring 225 is inserted into the gap 57 between the loadpins 19, 21. As illustrated in FIG. 12, each plate 248 is sandwichedbetween its respective ratchet wheel 235 and spiral load spring 225. Inthis configuration, as the ratchet wheels 235 are driven in thedirection of the arrow 250 (FIG. 11), the tab 236 will be drivenrotationally from surface A toward the surface B until it abuts thatsurface B. Thereafter, the ratchet wheels 235 are constrained to rotatein unison with the plates 248 and pins 19, 21, and no further load isapplied to the spiral load springs 225.

The embodiment of FIG. 13 is constructed and functions similarly to thatof FIGS. 11-12, the only difference being that each tab 336 of eachspiral load spring 325 engages its respective ratchet wheel 325 throughabutment with the bottom edge 338 of a “bump” 337, which is fixedlyattached to, or integrally formed as part, of each ratchet wheel 335.The embodiment of FIG. 14 is similarly constructed with the exceptionthat the tab 436 of the spiral load spring 425 is formed as a steppededge, which mates with a stepped opening 442 in the ratchet wheel 435.In various embodiments, the tab 436 may slide fit together with thestepped opening 442, may press-fit into that opening 442, or may bewelded in place in the opening 442.

From the foregoing, those skilled in the art will appreciate thatvarious adaptations and modifications of the just described illustrativeembodiments can be configured without departing from the scope andspirit of the invention. Therefore, it is to be understood that, withinthe scope of the appended claims, the invention may be practiced otherthan as specifically described herein.

What is claimed is:
 1. A method of providing strap tension adjustmentfor a tie down apparatus comprising: providing a rotatable drum surfaceconfigured to wind up a tie down strap and having a slot thereinconfigured to receive the tie down strap; providing a ratchet wheelcomprising a plurality of ratchet teeth and having an interior openingwith at least one inwardly protruding nub positioned thereon; mounting aspiral load spring having an outer tab and an inner leg adjacent theratchet wheel; causing the inner leg of the spiral load spring to rotatein unison with said rotatable drum surface; causing the outer tab ofsaid spiral load spring to rotate in unison with said ratchet wheel soas to load said spiral load spring; causing a nub engaging surface torotate in unison with said rotatable drum surface within said interioropening of said ratchet wheel so as to come into engagement with saidinwardly protruding nub as said ratchet wheel rotates such that theengagement between the inwardly protruding nub and the nub engagingsurface terminates loading of said spiral load spring.
 2. The method ofclaim 1 wherein termination of loading of said spiral load spring limitsan amount of pre-load force applied to said spiral load spring.
 3. Themethod of claim 1 wherein the interior opening of the ratchet wheelcomprises a circular surface on which said nub is formed.
 4. The methodof claim 3 wherein said plurality of ratchet teeth are circumferentiallydisposed around an outer surface of said ratchet wheel.